Substances in body fluids are being sought that stimulate fibrinogen synthesis in man and animals. The aim is to purify these, define them chemically, establish their mechanisms of action on fibrinogen synthesis and their role in the inflammatory process. Studies are being made on the role of the prostaglandins in the stimulation of fibrinogen synthesis. By means of thrombin labelled with radioactive iodine the sequential reactions of the various antithrombins with thrombin in flowing blood will be studied with the cellular mechanisms that remove thrombin-antithrombin complexes. Studies are being made on purifying antithrombin III and labelling it without denaturating by I125 so that its metabolism and regulation can be followed in man and animals. Computer models of various features of human salt and water metabolism and calcium and phosphate metabolism have been developed and their predictions are being tested against previously reported and on-going experiments.